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Compréhension et caractérisation multi-échelle de la rupture interfaciale d'assemblages collés (colle crash - tôle galvanisée) pour l'automobile

Abstract : The single lap-shear test is widely used by carmakers to characterize the adhesion of bonded joints. Two criteria govern the validation of the adhesion properties in the bonded joints: the shear strength and the failure mode which has to be cohesive. However, in some special cases, particularly when thin mild galvanized steel substrates were bonded with structural toughened adhesive, an interfacial pattern is obtained instead of cohesive failure. So the bonded assembly is not accepted even if its shear load at failure is high. A better understanding of the interfacial failure is required to adapt the carmakers specifications. The first objective of the PhD thesis was to analyze the critical phenomenon which favor the interfacial failure during single lap test. Substrate rigidity has significant effect on the failure pattern, because it influences the kinematic of deformation of the sample (rotation, steel plasticity, edge effect). Steel plasticity has been identified as a key factor for interfacial failure. The galvanized coating of the steel has a heterogeneous structure, which generate significant heterogeneous strain that could damage the interface. The second objective was to characterize the strength of the substrate-adhesive interface. Two methods have been proposed. The first one enable to measure the strength of an interface which homogeneous loading without edge effect (modified Arcan test). In the second method, the interface capability to resist to edge effects has been assessed. Thus, three different interfaces have been characterized using a three point bending test and thanks to an optical microscopy in situ analysis.
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https://tel.archives-ouvertes.fr/tel-01711967
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Submitted on : Monday, February 19, 2018 - 2:14:21 PM
Last modification on : Wednesday, September 16, 2020 - 9:57:02 AM
Long-term archiving on: : Sunday, May 20, 2018 - 12:23:19 PM

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  • HAL Id : tel-01711967, version 2

Citation

Jean Legendre. Compréhension et caractérisation multi-échelle de la rupture interfaciale d'assemblages collés (colle crash - tôle galvanisée) pour l'automobile. Mécanique des matériaux [physics.class-ph]. Université de Bretagne occidentale - Brest, 2017. Français. ⟨NNT : 2017BRES0076⟩. ⟨tel-01711967v2⟩

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